In the fields of civil engineering and architectural engineering, a laser rotary irradiating system for irradiating a laser beam for rotary scanning has been used to form a reference plane or a reference line. The positioning of a partition to be installed in a building or of lighting fixtures such as fluorescent lighting to be mounted on a ceiling is performed according to a setting-out line marked on a floor, and the position given by the setting-out line is determined by projecting it on the surface of the ceiling or the wall, etc. by a laser rotary irradiating system. The irradiating position of the laser beam is confirmed by an object reflector.
To align a reference plane formed by the laser rotary irradiating system with the setting-out line marked on the floor, a point vertically under the rotating axis of the laser beam of the rotary irradiating system main unit is aligned with a first reference point on the setting-out line, and the reference plane formed by the laser rotary irradiating system is aligned with at least one of a second reference point on the setting-out line far from the main unit.
In the conventional type laser rotary irradiating system as described above, after the laser beam reference plane formed by the laser rotary irradiating system is aligned with the setting-out line, it is not possible to detect by the laser rotary irradiating system itself whether or not the laser beam reference plane is aligned with the setting-out line during positioning operation. For this reason, if deviation occurs between the laser beam reference plane and the setting-out line, an error occurs in the positioning operation.
To solve the above problem, it is an object of the present invention to provide a laser rotary irradiating system, by which it is possible to detect by the laser rotary irradiating system itself the condition of alignment of the laser beam reference plane with the setting-out line during operation after the reference plane has been aligned with the setting-out line, and to improve reliability of the laser beam reference plane. Also, it is another object of the invention to provide a system, by which it is possible to reliably detect an object reflector without being influenced by external disturbance light in the detection of the object reflector.